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Astrophysics > Earth and Planetary Astrophysics

Title:
Solar System formation

Abstract: In this review, three major changes in our understanding of the early history
of the Solar System are presented.
1) Early differentiation: A few recent results support the idea that
protoplanet formation and differentiation occurred partly simultaneously than
CAI formation. First, some iron meteorites, eucrites, and angrites older than
the chondrules or even than the CAI have been found. Second, iron meteorites
could be debris of early disrupted differentiated planetesimals, scattered from
the terrestrial planet region to the Main Belt. Finally, chondrules contain
fragments of planetesimal material.
2) Earth and Moon: An equilibration mechanism explains the identical Oxygen
isotopic composition of the Earth and the Moon. In addition, it has been shown
that the Earth and the Moon mantles have the same 182^W anomaly, in contrast to
what was believed before. Consequently, the Moon forming impact should have
occurred after the extinction of the 182Hf radioactivity, about 60 Myr after
Solar System formation. This new datation is in agreement with new N-body
numerical simulations of the last phase of terrestrial planets formation, in
which giant impacts occur during about 100 Myr.
3) Giant planets and Nice model: The migration of the giant planets in the
protoplanetary disc can be prevented if the planets are in resonance, close to
each other. In the ``Nice model'', the 4 outer planets of the Solar System were
in a compact configuration after the dissipation of gaseous disc. A few hundred
million years later, a global instability drives the planets on their present
orbits, producing the Late Heavy Bombardment. In this frame, a lot of
characteristics of our Solar System can be explained.

Comments:

Invited review talk on Solar System formation, at the JENAM 2008 conference. Proceeding to appear in "Reviews in Modern Astronomy, 21"